By Meaghan Anderson
While most farmers are dealing with typical weed issues like waterhemp, giant ragweed, and annual grasses, some are finding new weeds in their crop fields. While kochia has been present in Iowa for some time, it has remained primarily a weed of railroads and unmanaged areas until recent years. This year we have received more reports in crop fields and have sent some for testing for herbicide resistance.
Kochia (Bassia scoparia) is an early germinating annual weed, and one of the driver weeds in the Great Plains states, especially in small grains. In Iowa, early tillage and herbicide applications have typically provided effective control in row crops but increasing herbicide resistance and reductions in tillage have allowed it to persist in some fields. While most kochia germinates early, seedlings can emerge through mid-summer.
The seedling stage of kochia is called ‘button’ stage; seedling leaves are covered with dense pubescence that can decrease absorption of foliar herbicides. As plants grow larger, key identification traits include alternate, linear leaves with hair and three prominent veins visible from the underside of leaves. Plants are often a blue-green or gray-green color and can grow to about 4-5 ft. tall. This species is a tumbleweed that breaks off at the soil surface in the fall to assist in further distribution of weed seed.
Like waterhemp, kochia is known for multiple herbicide resistances. Biotypes resistant to combinations HG 2, HG 4, HG 5, HG 9, and HG 14 exist in U.S. populations. The Get Rid of Weeds (GROW) integrated weed management group has a document dedicated to kochia and provides significant information on plant biology and management strategies.
Source : iastate.edu